One vertex per element, one color per generator, with an edge from x to x·s.
(1,2,5,4)(3,7,8,6)(9,10)(11,20)(12,23)(13,24)(14,19)(15,17)(16,21)(18,22)(25,26,31,28)(27,35,38,32)(29,39,37,33)(30,34,36,40)(1,3,5,8)(2,6,4,7)(9,11)(10,16)(12,22)(13,19)(14,18)(15,21)(17,20)(23,24)(25,27)(26,32)(28,35)(29,36)(30,37)(31,38)(33,40)(34,39)(10,17)(11,21)(12,19)(18,24)(26,28)(32,35)(33,39)(34,40) involution — undirected(9,12,15,19)(10,14,17,23)(11,22,21,13)(16,18,20,24)(25,28,31,26)(27,35,38,32)(29,39,37,33)(30,40,36,34)(9,13,15,22)(10,18,17,24)(11,19,21,12)(14,20,23,16)(25,29,31,37)(26,33,28,39)(27,36,38,30)(32,40,35,34)(1,4,5,2)(3,7,8,6)(9,14)(10,19)(11,18)(12,17)(13,16)(15,23)(20,22)(21,24)(25,30,31,36)(26,34,28,40)(27,37,38,29)(32,39,35,33)A Cayley diagram is a choice, not a fact about the group. Another drawing of this group — in a book, or on a different generating set — may look nothing like this one.